1. Field of the Invention
The present invention relates to a method for manufacturing a core mold for foam-molding to be used for foaming by steam heating a multitude of pre-expanded beads filled in a mold unit to produce a foam-molded article, provided with a concavo-convex pattern on its mold surface for forming a design pattern on the surface of the foam-molded article, and to the core mold manufactured by such a method.
2. Description of the Related Arts
In this technical field, for example, JP-A-H12-108134 discloses a method for manufacturing a core mold for foam-molding wherein a model is first fabricated by adhering a sheet material having a concavo-convex pattern to a wood mold, and then a sand mold is produced to which the concavo-convex pattern is transferred from the model, after which a core mold for foam-molding having a mold surface to which the concavo-convex pattern is transferred from the sand mold is constructed by casting.
However, this prior art has a disadvantage in that a design pattern formed on a foam-molded article thereby produced utilizing a core mold for foam-molding is blurred.
In addition, in order to remanufacture the core mold for foam-molding it is necessary to produce the sand mold each time, therefore manufacturing costs will inevitably be high and making the sand mold also requires a high skill level. Accordingly, the yield of manufacturing a core mold for foam-molding is not satisfactory at present.
In view of the foregoing disadvantages, an object of the invention is to provide a method for manufacturing a core mold for foam-molding by which an unblurred design pattern can be formed on a foam-molded article and manufacturing costs can be lowered, as well as the core mold manufactured by such a method.
To accomplish the foregoing object, the present invention provides a first method for manufacturing a core mold for foam-molding provided with a concavo-convex pattern on its mold surface for forming a design pattern on the surface of a foam-molded article, comprising the steps of forming a reverse concavo-convex pattern that is the reverse of the concavo-convex pattern on the surface of a core mold making model made of a conductive material having the same shape as the mold surface, and transferring the reverse concavo-convex pattern by electric discharge machining to the mold surface, thus forming the concavo-convex pattern on the mold surface.
A second manufacturing method according to the invention further comprises the step of executing a plurality of times the transference by electric discharge machining, each time changing the relative positions of the core mold making model against the mold surface.
In a third manufacturing method according to the invention, the core mold making model is made of graphite.
Also, the invention provides the first core mold for foam-molding manufactured by the first method of the invention, comprising a steam path disposed through a convex portion of the concavo-convex pattern.
The second core mold for foam-molding according to the invention comprises a plurality of adjoining components, wherein the core mold for foam-molding manufactured by the first method and/or the first core mold for foam-molding are employed as components.
The third core mold for foam-molding according to the invention further comprises a steam path disposed at a joint of the components.